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Hotspots of MLV integration in the hematopoietic tumor genome.

ABSTRACT: Extensive research has been performed regarding the integration sites of murine leukemia retrovirus (MLV) for the identification of proto-oncogenes. To date, the overlap of mutations within specific oligonucleotides across different tumor genomes has been regarded as a rare event; however, a recent study of MLV integration into the oncogene Zfp521 suggested the existence of a hotspot oligonucleotide for MLV integration. In the current review, we discuss the hotspots of MLV integration into several genes: c-Myc, Stat5a and N-myc, as well as ZFP521, as examined in tumor genomes. From this, MLV integration convergence within specific oligonucleotides is not necessarily a rare event. This short review aims to promote re-consideration of MLV integration within the tumor genome, which involves both well-known and potentially newly identified and novel mechanisms and specifications.

SUBMITTER: Tsuruyama T

PROVIDER: S-EPMC5340798 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Hotspots of MLV integration in the hematopoietic tumor genome.

Tsuruyama T T Hiratsuka T T Yamada N N

Oncogene 20161107 9

Extensive research has been performed regarding the integration sites of murine leukemia retrovirus (MLV) for the identification of proto-oncogenes. To date, the overlap of mutations within specific oligonucleotides across different tumor genomes has been regarded as a rare event; however, a recent study of MLV integration into the oncogene Zfp521 suggested the existence of a hotspot oligonucleotide for MLV integration. In the current review, we discuss the hotspots of MLV integration into sever ...[more]

PMID: 27721401

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Project description:The rapidly expanding information on the structural and functional characteristics of the human genome allows the development of genome-wide approaches to investigate the molecular circuitry wiring the genetic and epigenetic programs of clinically relevant stem/progenitor cells. Here, we define the transcriptional and epigenetic profile of human hematopoietic stem/progenitor cells (HSPC) and their committed, early myeloid and erythroid progeny. Cap Analysis of Gene Expression showed that the transcriptional state is largely maintained in the transition from early hematopoietic stem/progenitors to committed progenitor/precursors. A large fraction of differentially expressed active promoters in each cell type were classified as novel, possibly driving the expression of transcripts involved in HSPC commitment. Unannotated promoters harbored an enhancer chromatin signature, were enriched in cell-specific transcription factor binding sites, and were close to protein-coding cell-specific genes. To obtain a genome-wide description of regulatory regions, we performed ChIP-seq for histone modifications typical of promoters, enhancers and super-enhancers. ChIP-defined promoters were shared by HSPC and committed cells, whereas enhancer usage consistently changed upon commitment, thus indicating that the fine regulation of commitment is carried out by enhancer elements. The expression level of genes targeted by enhancers and super-enhancers was moderately higher in cells actively using these regulatory elements. However, functional annotation of targeted genes showed a low enrichment for cell-specific gene ontology categories. Finally, we used Moloney leukemia virus (MLV) to map functional regions of chromatin. Genomic regions targeted by MLV co-mapped with a fraction of epigenetically defined active regulatory elements, with two-third of MLV integrations falling in enhancers, and one-third in promoters. Most of MLV-targeted regulatory regions were differentially used between HSPC and their committed progeny. Analysis of the expression levels of promoters close to cell-specific MLV-targeted enhancers and functional assays indicated that MLV-defined regulatory regions are bona fide cell-specific enhancers. Finally, gene ontology analyses showed that MLV-targeted genes related to the peculiar cell identity. Overall, this study provided an overview of the differential transcriptional and epigenetic programs of HSPC and committed progenitors and represents a unique source of regulatory regions involved in HSPC commitment.

Project description:Murine leukemia virus (MLV) integrase (IN) lacking the C-terminal tail peptide (TP) loses its interaction with the host bromodomain and extraterminal (BET) proteins and displays decreased integration at promoter/enhancers and transcriptional start sites/CpG islands. MLV lacking the IN TP via an altered open reading frame was used to infect tumorigenesis mouse model (MYC/Runx2) animals to observe integration patterns and phenotypic effects, but viral passage resulted in the restoration of the IN TP through small deletions. Mice subsequently infected with an MLV IN lacking the TP coding sequence (TP-) showed an improved median survival by 15 days compared to wild type (WT) MLV infection. Recombination with polytropic endogenous retrovirus (ERV), Pmv20, was identified in seven mice displaying both fast and slow tumorigenesis, highlighting the strong selection within the mouse to maintain the full-length IN protein. Mapping the genomic locations of MLV in tumors from an infected mouse with no observed recombination with ERVs, TP-16, showed fewer integrations at TSS and CpG islands, compared to integrations observed in WT tumors. However, this mouse succumbed to the tumor in relatively rapid fashion (34 days). Analysis of the top copy number integrants in the TP-16 tumor revealed their proximity to known MLV common insertion site genes while maintaining the MLV IN TP- genotype. Furthermore, integration mapping in K562 cells revealed an insertion preference of MLV IN TP- within chromatin profile states associated with weakly transcribed heterochromatin with fewer integrations at histone marks associated with BET proteins (H3K4me1/2/3, and H3K27Ac). While MLV IN TP- showed a decreased overall rate of tumorigenesis compared to WT virus in the MYC/Runx2 model, MLV integration still occurred at regions associated with oncogenic driver genes independently from the influence of BET proteins, either stochastically or through trans-complementation by functional endogenous Gag-Pol protein.

Project description:BackgroundListeria monocytogenes is an important food-borne pathogen and model organism for host-pathogen interaction, thus representing an invaluable target considering research on the forces governing the evolution of such microbes. The diversity of this species has not been exhaustively explored yet, as previous efforts have focused on analyses of serotypes primarily implicated in human listeriosis. We conducted complete genome sequencing of 11 strains employing 454 GS FLX technology, thereby achieving full coverage of all serotypes including the first complete strains of serotypes 1/2b, 3c, 3b, 4c, 4d, and 4e. These were comparatively analyzed in conjunction with publicly available data and assessed for pathogenicity in the Galleria mellonella insect model.ResultsThe species pan-genome of L. monocytogenes is highly stable but open, suggesting an ability to adapt to new niches by generating or including new genetic information. The majority of gene-scale differences represented by the accessory genome resulted from nine hyper variable hotspots, a similar number of different prophages, three transposons (Tn916, Tn554, IS3-like), and two mobilizable islands. Only a subset of strains showed CRISPR/Cas bacteriophage resistance systems of different subtypes, suggesting a supplementary function in maintenance of chromosomal stability. Multiple phylogenetic branches of the genus Listeria imply long common histories of strains of each lineage as revealed by a SNP-based core genome tree highlighting the impact of small mutations for the evolution of species L. monocytogenes. Frequent loss or truncation of genes described to be vital for virulence or pathogenicity was confirmed as a recurring pattern, especially for strains belonging to lineages III and II. New candidate genes implicated in virulence function were predicted based on functional domains and phylogenetic distribution. A comparative analysis of small regulatory RNA candidates supports observations of a differential distribution of trans-encoded RNA, hinting at a diverse range of adaptations and regulatory impact.ConclusionsThis study determined commonly occurring hyper variable hotspots and mobile elements as primary effectors of quantitative gene-scale evolution of species L. monocytogenes, while gene decay and SNPs seem to represent major factors influencing long-term evolution. The discovery of common and disparately distributed genes considering lineages, serogroups, serotypes and strains of species L. monocytogenes will assist in diagnostic, phylogenetic and functional research, supported by the comparative genomic GECO-LisDB analysis server (http://bioinfo.mikrobio.med.uni-giessen.de/geco2lisdb).

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Hotspots of MLV integration in the hematopoietic tumor genome.

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Hotspots of MLV integration in the hematopoietic tumor genome.

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